Posted
by
timothyon Thursday July 01, 2010 @02:40PM
from the don't-hate-me-because-I'm-a-beautiful-spy dept.

sciencehabit writes with an intriguing story about the potential of figuring out where people have been by examining their hair: "That's because water molecules differ slightly in their isotope ratios depending on the minerals at their source. Researchers found that water samples from 33 cities across the United State could be reliably traced back to their origin based on their isotope ratios. And because the human body breaks down water's constituent atoms of hydrogen and oxygen to construct the proteins that make hair cells, those cells can preserve the record of a person's travels. Such information could help prosecutors place a suspect at the scene of a crime, or prove the innocence of the accused." Or frame someone by slipping them water from every country on the terrorist watchlist.

Well, one of Polish kings, Leszek Bialy, sent the pope an opinion of his medics that claimed that he suffers from an allergy to water, and, because during a campaign in Palestine an uninterrupted supply of beer or wine would be hard to assure, he can't go to the crusade there.

This may be forensically useful, but don't think of it like a fingerprint or a DNA match. There's only one degree of freedom here -- whether the water is isotopically "heavy" or "light". All of a person's water co9nsumption history is mixed up into one number.

So you won't be able to tell the difference between, say, a person who lived all year in Illinois (with a moderate isotope ratio) and a person who flies back and forth between Montana and Florida (who'd have a mix of "heavy" and "light" water in their system.)

So you won't be able to tell the difference between, say, a person who lived all year in Illinois (with a moderate isotope ratio) and a person who flies back and forth between Montana and Florida (who'd have a mix of "heavy" and "light" water in their system.)

Unless the technicians are clever enough to check multiple sections of the person's hair.

So you won't be able to tell the difference between, say, a person who lived all year in Illinois (with a moderate isotope ratio) and a person who flies back and forth between Montana and Florida (who'd have a mix of "heavy" and "light" water in their system.)

Not true. The fact that the oxygen isotopes are bound into hair means that we have some kind of a time reference.

Good point re the use of hair to provide a timeline, but if you figure the average human consumes about 1.5 kg of water a day, and contains about 60 kg of water, that means the water has a residence time of about a month and a half. It'll take that long to "flush out" your system.

And the "one degree of freedom" problem still limits the location accuracy of this. Check the map in the original article [acs.org]. The isotopic ratio of water is the same in Florida as in Texas; the same in Boston as in San Francisco.

Actually no! Check Figure 2 in the original article [acs.org]. Hydrogen and oxygen isotopes are linearly related to each other in natural waters, following the "Global Meteoric Water Line". If you measure delta-2H, you know delta-18O or vice versa.

This has been done before: in the investigation of the poisoning of Alexander Livinenko, the traces of Polonium 210 left wherever the poisoner(s) went gave the UK authorities a very detailed trail to work with - one that not only showed the exact teapot used for the poisoning, but also provides a fingerprint of where the Po-210 was produced and at what date.

I can see this science being abused. Whether your body contains a certain chemical signature or not is still circumstantial evidence, but increasingly our justice system (like many countries) are using it to give carte blanche access to a person's private information and life. Worse, if the request is later determined to have been falsified or exaggerated, the evidence gathered as a result of that request is still considered valid for the persecution of not just the original crime, but anything else uncovered as a result.

Thanks to shows like CSI and confidence in science, we want DNA samples, hair, urine, and a billion other things -- and believe that their presence somehow proves or disproves guilt. This is despite the fact that such evidence can be manufactured with ease -- the prime example being Photoshop for photographs, but virtually every technology you have around you can be used against you in some fashion or manipulated to imply or explicitly state something that is not true. Yet the courts rarely ask that samples be tested for contamination, or refuse to re-hear cases where the lab clearly and undeniably compromised the results.

It used to be that testimony was the primary vehicle in obtaining a conviction. Now we're increasingly using evidence that neither the judge, jury, defense, or even prosecution fully understands to take away other people's freedoms, sometimes under false pretext. While this particular technology is neither good nor bad, the system that will incorporate its use may be fundamentally flawed.

I drink a lot of water at work. But I have a gallon of water that rode with me on the 1000 mile trip to where I live now. It sits in my closet, on the off chance that my water goes off. I drink that, and I have a beautiful stripe of isotopes which indicate I spent a few days 1000 miles away.

Combine that with all the bottled water people drink, and all the pre-packaged drinks, and it's useless for much of anything. If I'm a mixture of water isotopes from Atlanta and Upst

I think it has potential uses, but its usefulness is wildly exaggerated in the article:

Such information could help prosecutors place a suspect at the scene of a crime, or prove the innocence of the accused.

Evidence that places someone in the general area of a city/region does not place them at the scene of a crime. Also, given the ease at which it can be manipulated, it certainly doesn't prove anything either.

Actually, I have heard that prosecutors hate CSI type shows because jurors want some technician to come in and say, "the pesticide oh his wheels indicate that he was at the farm at the time of the crime." Luck breaks like that only happen on... well, CSI.

I wish people would watch Law & Order more. Yeah, I'll sometimes sit through an episode of CSI but at the end of it, they always catch the murder and the murder always confesses at the end, saying they just had to kill or some other bullshit.

OTOH, L&O follows detectives around as they talk to one person who leads them to another and then they go back and, you know, acts like a detective. That and not every episode ends with "Yeah! we got that son of a bitch!" Some have been real downers which doe

Worse yet, since CSI came out forensic investigators have noticed a marked rise in the number of cases where Gloves and or Bleach were used at the scene of the crime. The Bleach is supposed to damage the DNA evidence they might leave behind.

Anyways if you want to game this system, do you drink water only where you live, and bring bottles filled at home with you, or just always buy bottled water and never drink tap?

As others have mentioned they'd probably get a lot of false positives from the local bottling

Source, when it comes to natural water, refers to the headwaters [wikipedia.org]. Thus, this sentence says that the isotope ratios of water vary depending on the minerals present in the ground where the water fell out of the air originally. The second sentence is poorly worded and should have said that the human body breaks down water into its constituent atoms of hydrogen and oxygen to construct the proteins. As a result, you can tell from the isotope ratio in the water where it fell originally.

1) Water at spring A has more calcium (a mineral) than water at spring B

2) Because of this, and some chemical processes, the water at spring A has a higher percentage of heavy water (deuterium oxide) than the water at spring B (this has a 50%+ chance of being incorrect, but let's stick with it for the example's sake)

3) Person X consumes water from spring A and person Y consumes water from spring B.

4) The metabolisms of the two persons break down the water and put it into the proteins in their respective cel

Nope. Different isotopes of the same element have the same chemistry, so chemical processes won't alter isotope ratios. This is an important feature of using isotopes as tracers, since generally the tracer elements will be subject to a lot of chemical processes -- like being absorbed into the body and incorporated in to hair.

It turns out that TFA (which is just a bad summary of an actual paper) appears to have introduced the "minerals" bit. Minerals aren't involved; different water sources just have differe

And what if the minerals at the source of the water are appreciably the same? Reliably being tracked back to a handful of collection sites across the US doesn't exactly equate to "placing someone at the scene of a crime".

If you look at the heat map included with the article, the entirety of Florida is indicated as having the same expected water composition. Similarly for most of Texas, and wide swaths of the Midwest / Central US.

So if someone commits a crime in Tallahassee, and I buy bottled water at

And because the human body breaks down water's constituent atoms of hydrogen and oxygen to construct the proteins that make hair cells, those cells can preserve the record of a person's the travels of things people drink.

Fixed that for you. This would work if we didn't ship products throughout the country. Get pulled over for a DUI, "Couldn't have been me, check my hair! I've been in Fort Collins!"

I mean, sure, the bottled water will have the same signatures, but what is to say you didn't drink your own bottled water wherever you went? Or things like bottle sodas, and drinks. The best you might be able to do is say that they had drink which used water from XYZ location. It is a far stretch to say that they were in XYZ when they drank it. Heck, there are stores around me which sell bottled water from around the world, and I know I have even tried a few, but I never left my home town, yet it according to this "evidence" I have been to Australia, New Zealand, Germany, Ukraine, Ireland, and Poland...

To be fair, they do attempt to address that, though they do so only in the average case. Actually a big part of the paper [acs.org] is exactly that: an attempt "to assess the links between purchase location and the isotopic composition of beverages" and given that purchase location may not be the same as bottling location, whether or not "these beverages could have a confounding impact on the overall isotopic composition of a consumer’s fluid intake".

Congratulations for coming up with the same obvious problem everyone else did. Did you, by any chance, read the part of the paper where they discuss this problem and its ramifications and then test how well the isotope ratios in tap water function as a proxy for the isotope ratios in purchased bottled beverages?

If you only drink mainstream bottled beverages, wouldn't that rule out any local factor in what you are drinking? "Well, he looks like he was drinking some beer brewed in Ireland..." Similarly, Dasani/Sparkletts/Arrowhead all have relatively large sales areas, don't they?

So what if it does? I know, you think you're being funny, but really. They won't be isotopes indicative of where I am or live, will they? They'd be indicative of whatever water source the distiller (Niagara, DS Waters) is using. So DHS would wind up sending the troops to some place on the other side of the country.

Yeah it was a joke, intended to point out that "isotopes of hydrogen and oxygen" are not removed by distilling the water, because the water is made up of those "isotopes of hydrogen and oxygen."

Most bottled water you buy is bottled very near to the point of purchase, so it would still probably give a decent location as long as the signature was good enough to not provide 500 possible matches.

As has already been discussed ad nauseam here, the technique as described wouldn't allow them to track your location

Most things you drink aren't bottled in your home town. (Including bottled water, if you're into that sort of thing.)

If somehow this technique were to be come a common defense tool, then someone planning a crime could shrewdly stockpile tap water from a city with a distinct signature that isn't where the crime will take place.

It might be marginally useful as a tool in a civil case if you want to convince the jury where someone was (but probably not if you want to convince them where he/she wasn't); I would hope it would be considered too inconclusive to be used in a criminal trial.

If somehow this technique were to be come a common defense tool, then someone planning a crime could shrewdly stockpile tap water from a city with a distinct signature that isn't where the crime will take place.

I'd be impressed if you could stockpile significant amounts of water without leaving evidence in the form of empty containers, palates of water, shipping receipts, purchase receipts, and loyalty card information.

It's not that hard to destroy evidence. The hard part is destroying evidence without creating even more evidence.

Depending on your situation, it may not be that hard. For example, the city of Minneapolis, MN gets its water supply for the Mississippi River. A few miles away, most of the southern suburbs get their water from the Jordan and Prairie Du Chien-Jordan aquifers. On one hand, that may make it easier to pinpoint where someone is from, but on the other hand it also means I would not have to travel far to get water from a very different source.

Well, there sort of is. Hair grows at the root only, so if I watch how the patterns change moving from the root of a hair to the tip, I can get a fuzzy sort of timeline of your waters' origin. Circumstances where that's precise enough to be useful, though, seem narrow.

Uh... the USG claims you went to Afghanistan to train with terrorists for a month, you just went to London like your last ticket purchased in the US says... then you use the hair.

If the hair says London, the government knows you either had a massive water truck with you or that you are telling the truth. OTHO, if the hair says Afghanistan then they have circumstantial evidence and might have caught you in a lie. In the end, it's better screening out than in or catching people in lies.

Yeah, you also have to think about how much of your water comes from drinking water and how much comes from food. Most food is local (especially things like bread), but even produce is often not from that far off (bananas excluded, obviously).

Most food is not local, not even close. Take a look at the small print when you're at the supermarket; around here (central NY state) most of it, especially during the winter and spring, comes from places like California, Florida, Mexico, Argentina, even China. Bread is one of the few exceptions (and the wheat isn't grown locally, either).

I'd say the "identifying where a bottle of water is from" part may have some scientific validity. Assuming that the isotope ratios in the oxygen molecules in your blood match the water you're drinking is more dubious - you're also breathing air, which may have different ratios, plus your body would also be exchanging liquids between cells and bloodstream, so there's a long slow storage period. How that relates by the time the stuff gets out to your hair is even more speculative. The real question is how

I've got a big collection of bottled water from a lot of different countries because I like the labels on them. I see a potential use for them now.

Dude, don't drink them! They're valuable! Do you know how hard it is to get illicit liquids like water into the US these days?

I had bottled water in my checked luggage seized last time I flew back from South America... maybe they thought I might have dissolved drugs in them or something. I figured it was better to let them keep them than ask for the water b

This is so super awesome, I'm going to move to a 3rd word slave state to ensure I get the most oppressive experience possible.

That is quite unnecessary; the officials in all Western states are working hard to bring the 3rd world here. All we have to do is lose a few more jobs and repeal minimum wage laws and I think we're all set.